The present invention relates to an electro-optical device, in which deterioration of the display quality caused by so-called horizontal crosstalk can be prevented, a circuit for driving the electro-optical device, a method of driving the electro-optical device, and an electronic apparatus.
Generally, in a liquid crystal panel, which provides a desired display using an optical change of an electro-optical material such as liquid crystal, the liquid crystal is interposed between a pair of substrates. Such liquid crystal panels can be classified into several types depending upon a driving method. For example, in an active matrix type driving method, in which pixels are driven by three-terminal switching elements, a configuration described below is provided. Of a pair of substrates constituting such a liquid crystal panel, a plurality of scanning lines and a plurality of data lines are provided so as to intersect with each other on one of the substrates. A pair of a three-terminal switching element such as a thin-film transistor and a pixel electrode is provided formed at each of intersections of the scanning lines and the data lines. Peripheral circuits for driving the scanning lines and the data lines are provided around a region in which the pixel electrodes are provided (display region). On the other substrate, a transparent counter electrode (common electrode) opposing the pixel electrodes is provided, which is maintained at a constant voltage. Further, on the opposing surfaces of the substrates, alignment films which have been rubbed so that the longitudinal axis of the liquid crystal molecules are gradually twisted between the substrates, for example, by approximately 90 degrees. In addition, on the outer surfaces of the substrates, polarizers corresponding to the alignment directions are provided, respectively.
Each of the switching elements provided at the intersections of the scanning lines and the data lines is turned on when a scanning signal applied to the associated scanning line becomes active level, supplying an image signal sampled by an associated data line to the pixel electrode. Thus, to a liquid crystal capacitor formed of the pixel electrode, the counter electrode, and the liquid crystal interposed between the pixel electrode and the counter electrode, a voltage difference between the voltage on the counter electrode and the voltage of the image signal is applied. Even if the switching element is turned off thereafter, the liquid crystal capacitor maintains the voltage difference already applied due to its own capacitance and the capacitance of a storage capacitor.
Light passing between the pixel electrode and the counter electrode is rotary (circularly) polarized by approximately 90 degrees corresponding to a twist of the liquid crystal molecules if the effective voltage applied across the two electrodes is zero. As the effective voltage increases, the liquid crystal molecules tilt toward the direction of the electric field, which results in loss of the optical rotatory. Thus, for example, in a transmissive type liquid crystal display, when polarizers in which polarization axes are orthogonal to each other corresponding to the alignment directions respectively are formed on an incident side and a back side (in a normally white mode), and when the effective voltage applied across the two electrodes is zero, light is transmitted and white is displayed (transmittance is large). As the effective voltage applied across the two electrodes increases, transmitting light is blocked and finally black is displayed (transmittance is small). Accordingly, a predetermined display can be performed by controlling the voltage applied to the pixel electrode for every pixel.
However, the above-mentioned liquid crystal panel suffers from the problem of deterioration of the display quality caused by so-called horizontal crosstalk. The horizontal crosstalk herein refers to the case in which, when a rectangular black region is displayed in a window over a gray background in the normally white mode, for example, as shown in FIG. 12, a gray region on the right (in a horizontal scanning direction) of the black region becomes brighter (or darker as the case may be) than the original gray color, and then gradually returns to the original gray color. In FIG. 12, a gray scale is represented by the line density of oblique lines (the same is applied to FIG. 13).
Such a horizontal crosstalk may be solved up to a certain degree by a technology in which a swing potential on the counter electrode is added to the image signal which is supplied to the pixel electrode.
However, the above-mentioned horizontal crosstalk may be suppressed up to a certain degree, but another horizontal crosstalk is generated. The horizontal crosstalk refers to the case in which, when the black region is displayed in the window over the gray background, for example, as shown in FIG. 13, in a region which is adjacent to the black region in a horizontal direction among the region of the gray background, a region displaced by one row in a vertical scanning direction becomes brighter than the black region.